1. Field of the Invention
This invention relates to medical articles, and more particularly, relates to an article having a hemocompatible coating permanently affixed to a blood-contacting surface of the article.
2. Background
There are many applications in the medical device industry where it is desirable that a blood-contacting surface be both compatible with blood and antithrombogenic. Exemplary of such devices is blood collection tubes. Blood samples are routinely collected in glass evacuated tubes. One end of a double-ended needle is inserted into a patient""s vein. The other end of the needle then punctures a septum covering the open end of the tube so that the vacuum in the tube draws the blood sample through the needle into the tube. Using this technique, a plurality of samples can be taken using a single needle puncture of the skin.
In addition, recent advancements in analytical instrumentation have made it possible to carry out a variety of hematological or chemical diagnostic procedures on very small quantities of blood, such as may be obtained by puncture of a patient""s finger, earlobe or an infant""s heel. Accordingly, a variety of blood sample microcollection devices have been disclosed in the art.
Plastic tubes have been proposed for blood collection. Plastic offers a number of advantages over glass such as lower breakage, less weight in shipment, and easier disposal by incineration. However, plastics are generally hydrophobic, and blood does not flow smoothly over hydrophobic surfaces. Instead, blood components, such as platelets, fibrin or clotted blood thus generally adhere tenaciously to plastic surfaces and hang up on the walls of plastic collection tubes. This is a particular problem in small diameter gravity actuated microcollection tubes during sample collection or in vacuum tubes during subsequent centrifugation. Thus, in any collection apparatus, it is highly advantageous if the collection tube has a surface which resists adherence to blood components at any stage of the collection process or any subsequent analysis procedure.
Adherence of blood components generally is not a problem with glass articles, and accordingly, one approach to overcoming this problem in plastic has been to modify the plastic surface to be more glass-like, i.e., to present a hydrophilic surface to the blood. To this end, plastic collection tubes have been treated with a gas plasma to alter the surface chemistry by introduction of heteroatoms. In another approach, the interior wall surface of the plastic tube has been modified by coating with materials such as surface-active agents, water-soluble polymers or water insoluble polymers carrying hydrophilic coatings. For example, U.S. Pat. No. 6,077,235 discloses a blood collection tube in which permanent non-adherence is achieved by blending a hydrophilic-hydrophobic copolymer into the tube polymer.
While the above disclosures have improved blood flow and reduced adherence of blood components to plastic articles, the problem has not been totally solved because the coatings applied to the prior art surfaces are partially or completely removed by the blood so that the surfaces revert back to hydrophobic. There is a need for an article and method therefor which would prevent adherence without introducing any foreign material into the plasma, serum or clot until the intended medical procedure is complete.
A medical article having a blood-contacting surface includes a plastic substrate having a hydrogel permanently affixed to the blood-contacting surface. In this disclosure the term hydrogel is used to designate a crosslinked polymeric coating on the substrate surface, and the term hydrophilic polymer is used to designate the material which upon crosslinking gives the hydrogel.
A preferred article is an evacuated polyethylene terephthalate (PET) blood collection tube fitted with a puncturable stopper, and the preferred hydrogel is polyvinyl pyrrolidone (PVP) bound to the inside wall surface of the tube by electron beam or gamma irradiation.
The hydrogel coating becomes lubricious by absorption of water when in contact with blood, and thereby prevents blood components from adhering to the article. Because the hydrogel is permanently affixed to the article surface, it cannot be washed away by contact with the blood. Further, the coating is applied without use of any environmentally unfriendly solvents, many of which cause plastics to become cloudy and may interfere with visual or instrumental observation of the contents. Finally the article may be sterilized by the radiation used to crosslink the polymer and bind the resulting hydrogel to the substrate.